A technique of display control in a case where plural windows overlap each other is known, as described in JP-A-8-161139. JP-A-8-161139 discloses, for example, in a case where at least two windows are displayed on a display screen so that the two windows partly overlap each other, replacing a window in the foreground with a window in the background at predetermined intervals of time, and determining for each window a length of time to display the window in the foreground, depending on the length of time for which the window is used.